NOAA satellite and air-borne sensing of a small-scale, coastal tidal jet

Abstract

Koombana Bay, on the south-west coast of Australia, contains a tidal jet that emanates from Leschenault Inlet via a man-made channel 150 m wide. The tides are of mixed diurnal-semidiurnal character. The strongest jets are induced by the diurnal tide and flow at night in summer and during daytime in winter. The duration of the discharge is about 9 h, after which the maximum length of the jet is a few kilometres. Extensive field studies together with numerical and analytical modelling have recently been completed on the jet. These allowed predictions of optimum times for viewing the jet via an air-borne thermal scanner aboard the CSIRO Fokker F27 aircraft, and a NOAA7 satellite image. The air-borne image mapped the late-summer jet, which consisted of night-cooled water from the shallow Inlet. Because the satellite pass occurs in late afternoon, the seasonality of the tide limits visibility of the jet in the imagery to late winter. The NOAA7 image shows a jet composed of warm water that has been heated during the day inside the Inlet. These observations confirm the sea data and model results and are believed to be the first use of NOAA imagery to resolve a coastal oceanographic feature of this scale.